ORIGINAL ARTICLE

Soft Tissue and Bony Injuries Attributed to the Practice of : A Biomechanical Analysis and Implications for Management

Melody Lee, MD; Elizabeth A. Huntoon, MD, MS; and Mehrsheed Sinaki, MD, MS

Abstract

Objective: To analyze injuries that were directly associated with yoga practice and identify specific poses that should be avoided in patients with osteopenia or osteoporosis. Patients and Methods: We retrospectively reviewed the medical records of patients with injuries that were primarily caused by yoga. Patients were seen from January 1, 2006, through December 31, 2018. Injuries were categorized into 3 groups: (1) soft tissue injury, (2) axial nonbony injury, and (3) bony injury. Patients underwent evaluation and were counseled to modify activity. Results: We identified 89 patients for inclusion in the study. Within the soft tissue group, 66 patients (74.2%) had mechanical myofascial pain due to overuse. Rotator cuff injury was seen in 6 (6.7%), and trochanteric bursopathy was observed in 1 (1.1%). In the axial group, exacerbation of pain in degenerative joint disease (46 patients [51.7%]) and facet arthropathy (n¼34 [38.2%]) were observed. Radiculopathy was seen in 5 patients (5.6%). Within the bony injury category, kyphoscoliosis was seen on imaging in 15 patients (16.9%). Spondylolisthesis was present in 15 patients (16.9%). Anterior wedging was seen in 16 (18.0%), and compression fractures were present in 13 (14.6%). The poses that were most commonly identified as causing the injuries involved hyperflexion and hyperextension of the spine. We correlated the kinesiologic effect of such on specific musculoskeletal structures. Conclusion: Yoga potentially has many benefits, but care must be taken when performing positions with extreme spinal flexion and extension. Patients with osteopenia or osteoporosis may have higher risk of compression fractures or deformities and would benefit from avoiding extreme spinal flexion. Physicians should consider this risk when discussing yoga as exercise. ª 2018 Mayo Foundation for Medical Education and Research n Mayo Clin Proc. 2019;94(3):424-431

oga is an ancient practice believed to turning to their primary care physicians for have originated over 5000 years ago, guidance regarding yoga safety, it is important For editorial Y with the first mention of it in the Rig for physicians to be aware of the risks and ben- comment, see Veda, one of the oldest sacred Indian texts. efits of yoga. page 385; for The practice flourished and gave rise to many The benefits of yoga in terms of flexi- related article, see distinct variations, eventually being brought bility, strength, and balance are widely page 432 to the Western world in 1893 when the young known. Many health care professionals From the Department of introduced yoga at have encouraged the practice of yoga, tout- Physical Medicine and Reha- the World’s Parliament of in Chi- ing it as a safe exercise for patients at bilitation, Mayo Clinic, 1 1,4,5 Rochester, MN (M.L., M.S.); cago. Since then, yoga has gained immense different levels of health. However, mul- and Department of Physical popularity as a form of exercise and relaxation. tiple reports have described injuries result- Medicine and Rehabilitation, Nationally representative studies in the United ing from yoga, ranging from mild muscle Virginia Commonwealth Uni- 6,7 versity, Richmond, VA States have reported that the 12-month preva- strains to bony fractures. For osteoporotic (E.A.H.). lence of yoga practice has increased from 3.8% and osteopenic patients in particular, the re- in 2004 to 8.9% in 2016, with a lifetime preva- ports of bony injuries raise concerns that lence of 13.2%.2,3 With patients increasingly warrant further investigation.

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With some exceptions, the literature to rest were from across North America. Base- date does not appear to recommend suffi- line patient characteristics are shown in cient caution or accommodations for yoga Table 1. The patients had various age-related in patients with impaired bone integrity.4 comorbid conditions, such as hyperlipid- Some authors even suggest yoga as an excel- emia, , and osteoporosis. Our lent exercise for patients with osteopo- rosis.5,8 Little to no guidance is available regarding maneuvers that are potentially TABLE 1. Baseline Characteristics of the 89 Study dangerous. Our primary aim in this study Patientsa was to identify patients who were injured Characteristic Value while practicing yoga and to determine the Age (y) specific poses that caused their injuries. We Mean SD 58.313.6 defined injury as musculoskeletal pain or Range 21-87 discomfort severe enough for a patient to Female sex 80 (89.9) seek physician evaluation. Our secondary Height (cm) aim was to identify poses that should be Mean SD 165.68.6 avoided based on these results and kinesio- Range 145.5-188 logic principles, particularly for patients Weight (kg) with underlying osteopenia or osteoporosis. Mean SD 74.314.3 Our goal is to provide guidance to physicians Range 50.5-89.0 b who care for patients who practice yoga. Pain score Mean SD 6.22.6 Yoga has many benefits, but it is by no Range 0-10 means a completely benign form of exercise, T score (n¼43) and caution is warranted when counseling Mean SD 2.051.24 patients on its practice. Range 1.1 to 4.7 Working status PATIENTS AND METHODS Retired 30 (33.7) This study was approved by the Mayo Clinic Working full-time 37 (41.6) Institutional Review Board. We retrospec- Working part-time 3 (3.3) tively reviewed the medical records of pa- On disability 1 (1.1) Homemaker 12 (13.4) tients with injuries that were primarily Student 2 (2.2) caused by yoga. The study cohort consisted Unemployed 4 (4.4) of patients who had been referred to the Comorbid conditionsc musculoskeletal clinic by their primary care 24 (27.0) physicians for evaluation of the etiology of Osteoporosis 22 (24.7) their pain. All patients had been referred to Hyperlipidemia 23 (25.8) the senior author (M.S.), who has special in- Osteopenia 19 (21.3) terest in osteoporosis and musculoskeletal Headache 11 (12.4) Hypertension 13 (14.6) health. Patients were seen from January 1, Hypothyroidism 14 (15.7) 2006, through December 31, 2018. Clinical Depression 12 (13.5) characteristics of patients in the cohort Vitamin D deficiency 10 (11.2) were obtained retrospectively from their Anxiety 8 (9.0) health records. Marital status Married 72 (80.9) RESULTS Divorced 8 (9.0) Single 7 (7.9) Patient Characteristics and Evaluation Widowed 2 (2.2) We identified 89 patients for inclusion in aData are presented as No. (percentage) of patients unless this series. Of these, 37 (41.6%) resided indicated otherwise. bPotential pain scores ranged from 0-10. within the same state as our clinic, 1 was c Some patients had more than one comorbid condition. from Panama, 1 was from India, and the

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body height and were determined to be de TABLE 2. Location of Pain at Initial Evaluation novo based on magnetic resonance imaging ¼ a Location No. (%) (N 89) and comparisons of prior radiographs, Cervical spine 23 (25.8) computed tomographic images, or positron Thoracic spine 30 (33.7) emission tomographic scans. Within the Lumbar spine 53 (59.6) soft tissue group, 66 patients (74.2%) had Sacral spine 22 (24.7) mechanical myofascial pain due to overuse. Shoulders 19 (21.3) Rotator cuff injury was seen in 6 (6.7%), Hips 10 (11.2) and trochanteric bursopathy was observed Thighs 4 (4.5) in 1 (1.1%). In the axial group, exacerbation Knees 5 (5.6) of pain in degenerative joint disease (46 pa- ¼ Feet or ankles 3 (3.4) tients [51.7%]) and facet arthropathy (n 34 Elbows 1 (1.1) [38.2%]) were observed. Radiculopathy was Wrists 1 (1.1) seen in 5 patients (5.6%). Within the bony injury category, kyphoscoliosis was seen on aSome patients had pain at more than one location. imaging in 15 patients (16.9%). Spondylolis- thesis was present in 15 patients (16.9%). Anterior wedging was seen in 16 (18.0%), patient population had a higher rate of oste- and compression fractures were present in oporosis than the general American popu- 13 (14.6%). Of note, 12 of the patients lace, with 24.7% (22 of the 89 patients) with vertebral compression fractures were having documented osteoporosis as opposed included in previous reports.7,10 In this to the estimated 10.3% prevalence in the 9 study, we further analyzed their exercise United States. The youngest patient had programs and identified the poses that Ehlers-Danlos syndrome. The patients were were blamed for their injuries. We also iden- otherwise generally healthy and enjoyed be- tified yoga-related anterior wedging in 16 pa- ing active, participating in other nonstrenu- tients, which has never been described ous exercises such as tai chi or . before. All bony injuries appeared to be Many patients reported pain in the back, related to yoga exercises involving spinal neck, shoulder, hip, and knee (Table 2), and flexion, as described by the patient. many had multiple areas of discomfort. Appropriate imaging and evaluation were pursued. During the evaluation, when asked about exercises or movements that incited TABLE 3. Type of Injury Caused by Practicing Yoga, or exacerbated their symptoms, all patients as Determined by Clinical Findings and Radiologic identified yoga as the primary cause or aggra- Evidence vating factor. Many were able to specify which Injurya No. (%) (N¼89) poses were particularly painful (ie, induced Soft tissue their presenting symptoms). Patients were Mechanical myofascial pain 66 (74.2) counseled in activity modification. (due to overuse) Rotator cuff tendinopathy 6 (6.7) Trochanteric bursopathy 1 (1.1) Yoga-Associated Injuries Axial Injuries were determined by clinical findings Facet arthropathy 34 (38.2) and radiologic evidence. All imaging was Degenerative joint disease 46 (51.7) interpreted by the attending radiologists. Radiculopathy 5 (5.6) The injuries were then categorized into 3 Bony groups: (1) soft tissue injury, (2) axial nonb- Spondylolisthesis 15 (16.9) Kyphoscoliosis 15 (16.9) ony injury, and (3) bony injury. Table 3 Wedging deformity 16 (18.0) summarizes the injuries observed in each Compression fracture 13 (14.6)

category. All compression fractures were a Some patients had more than one type of injury. defined as a 20% or greater loss in vertebral

426 Mayo Clin Proc. n March 2019;94(3):424-431 n https://doi.org/10.1016/j.mayocp.2018.09.024 www.mayoclinicproceedings.org SOFT TISSUE AND BONY INJURIES ATTRIBUTED TO YOGA

FIGURE 1. Patient-reported yoga poses that led to injury. Used with permission of Mayo Foundation for Medical Education and Research.

Patients identified 12 yoga poses that compression fracture (Figure 3). Interval caused injuries (Figure 1). Most patients change was observed when comparing imag- identified at least 2 poses that caused or aggra- ing from earlier in the year. vated their symptoms. The most commonly Of the 89 patients, 22 (24.7%) returned identified poses involved either hyperflexion for follow-up (range, 2 days to 5 years), or hyperextension. Figure 2 shows the num- including 5 patients with vertebral compres- ber of injuries associated with each pose. As sion fractures. All patients who were able to an example, one patient had acute thoracic successfully modify their activities reported back pain while performing pose E. She improvement or resolution of their symp- initially attributed it to a “pulled muscle” toms. We also received multiple communi- because she had practiced yoga for many cations from patients who were unable to years without incident. However, she had return for follow-up, saying that their pain persistent and severe pain (rated 9 of 10 on improved after modifying their yoga. The 7 the pain scale, with 10 representing maximal patients who declined the recommendations pain), and radiography revealed a T10 to avoid the aggravating positions continued

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With yoga gaining popularity in recent 45 40 years, yoga-related injuries have also become 35 increasingly common. Although the patients 30 in our series were evaluated between 2006 25 20 and 2018, the median year of evaluation 15 was 2015.

No. of injuries 10 5 0 DISCUSSION ABCDEFGH I JKL In this study, the most commonly seen in- Yoga pose juries were soft tissue, mechanical, and musculoskeletal injuries related to poor FIGURE 2. Number of injuries associated with each yoga pose depicted in posture. Patients with degenerative disk dis- fi Figure 1. Some patients identi ed more than one position that caused injury ease or facet arthropathy experienced exacer- or exacerbated symptoms. bation of their symptoms after certain yoga poses, particularly extremes of flexion and extension. These findings are consistent to experience the same symptoms, with the with the current literature. A recent system- exception of 1 patient who had spontaneous atic review found that soft tissue injuries improvement. (eg, strains, sprains) were the most common Our patients had varying levels of yoga 11 injuries reported with the practice of yoga. experience. Some had just started, whereas Technique may be a factor in some of the in- others had been practicing for years. Tech- juries, but in our case series, many of the pa- nique could not be verified because we tients had been practicing yoga for years and were not observing the patients in a labora- had never had any issues with it. tory setting. Many of these patients had Another recent prospective cohort study been doing yoga as routine exercise for a that surveyed 2 suburban yoga centers long time because previously it had been described 19 patients who had development helpful to them. of new pain in 23 different areas during class.12 The reported results appear to be consistent with our findings, with patients being able to directly identify incident events while prac- ticing yoga and often identifying multiple painful areas. The patients in our soft tissue injury and axial nonbony injury groups are likely similar to the suburban patients who had pain while practicing yoga. However, our studies do have some meaningful differences, beyond study design. In our study, we described pain and confirmed the injuries through medical examination, radiographic evidence, and medical record documentation. We also describe 29 bony injuries, which is, to our knowledge, the largest description of yoga-induced vertebral injuries to date. Addi- tionally, we identify specific poses that should FIGURE 3. A, Baseline thoracic radiograph of a 55-year-old woman with be avoided in patients with osteopenia and osteopenia (T score, 1.8). The patient was otherwise healthy and enjoyed osteoporosis. long-distance running and yoga. B, Thoracic radiograph of the same patient The severity of yoga-induced injuries later that year showed a T10 vertebral compression fracture (arrow). The likely represents a continuum. Although the patient had experienced severe thoracic back pain when performing pose E 12 in Figure 1. study by Campo et al was performed at a community level, our patients were seen at a

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musculoskeletal specialty clinic at a tertiary exceed the body’s biomechanical compe- referral center. We likely see patients at the tence, resulting in injury ranging from liga- very extreme end of the continuum, ie, mentous sprain to wedging deformity and patients who are seeking medical help after even compression fracture, as evidenced in having considerable pain and discomfort. If this case series. patients had been counseled on which poses Although spinal flexion exercises were the to avoid, such injuries potentially could most commonly identified causes of injury in have been avoided. this study, many patients also reported pain Regular exercise is integral for bone or were found to have injury with extreme hy- health and general conditioning,13-16 and perextension of the spine (Figure 1H is one all patients in this study reported starting example). With hyperextension, the weight yoga for its perceived health benefits. How- of the upper body exerts torque on the poste- ever, yoga can push the body to the limits rior spine, and these compressive forces are of biomechanical competence. Poses that mostly being absorbed by the ligamentous required end-range flexion (Figure 1B, 1D, structures, facet joints, and posterior interver- and 1E) most commonly initiated or aggra- tebral disks. These forces can be translated vated pain. We noted that more serious in- into the lumbar spine, leading to injury. juries, including wedging deformity and Extreme hip extension can also induce labral vertebral fractures, could be directly traced strain. If the head is not controlled and held in back to certain yoga positions. Almost all full extension, the cervical spine can also be the severe injuries were related to extremes involved. of spinal flexion and extension (particularly Most patients in this series were women (80 flexion). Spinal flexion exercises in yoga of the 89 patients [89.9%]), a finding consistent encourage spine flexibility through paraspi- with surveys reporting that women practice nal muscle relaxation and of spi- yoga more commonly than men.2,3 Women nal ligaments. Although a healthy spine are also more affected by osteoporosis and can tolerate such postures with ease, an oste- osteopenia than men because of the changes oporotic or osteopenic spine may have diffi- associated with hormonal differences.20 Start- culty translating the forces. Avoiding such ing in puberty, women develop less muscula- positions appeared to improve symptoms ture than same-size male controls, leading to and relieve pain. fewer stabilizing forces in the spine.21,22 Thus, According to spine kinematics, extreme it is expected that more women than men are spinal flexion exercises increase torque pres- symptomatic. In addition, most women in this sure to the vertebral bodies. Some pressure study were postmenopausal. is transferred to the intervertebral disks, Our study has some limitations, including whereas the remainder is absorbed by the generalizability because our patients were vertebral body.7 The pose shown in seen at a specialty clinic in a tertiary care Figure 1B loads the anterior cervical spine, center. However, it is still important to note and that in Figure 1D can load the midthora- that serious injuries are possible with the cic, thoracolumbar, and upper lumbar spine. practice of yoga. We are also limited with re- Most vertebral compression fractures occur gard to follow-up. The effects of activity in those areas.17,18 In the pose shown in modification were known for only 22 pa- Figure 1E, the weight of the body is also added tients. Our facility is a tertiary referral center, in a closed kinetic chain, multiplying the with most patients in the study living out of amount of pressure that the vertebral body state. We also do not routinely see return pa- must withstand. This compressive load can tients unless they have continued symptoms usually be tolerated by a competent spine, despite our recommendations. Monitoring but in the setting of osteoporosis, osteopenia, the patients’ clinical status over a longer or age-related degenerative arthropathy, the period could yield further insight. Addition- properties of soft and bony tissues are altered ally, the patients’ duration of participation and often weakened.19 Such exercises can in yoga was not clearly defined. It would be

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interesting to determine whether new practi- of yoga, and appropriate exercise programs tioners are more prone to injury than more should be recommended on a case-by-case experienced or whether patients prac- basis. ticing at home without trained instructor su- pervision are more likely to report injuries. ACKNOWLEDGMENTS However, such investigations were outside We thank Dr Karl , Editor-in-Chief of the scope of our study. Mayo Clinic Proceedings, for his thoughtful re- Given the observational nature of the view of the original manuscript, constructive study, causation cannot be definitely deter- criticism, and subsequent recommendations. mined. However, it is impossible to ignore the fact that every patient included in this case series identified yoga as the sole cause Potential Competing Interests: The authors report no or exacerbating factor of their pain. These in- competing interests. juries are occurring, and it is important that clinicians are aware that yoga, as with any Correspondence: Address to Mehrsheed Sinaki, MD, MS, Department of Physical Medicine and Rehabilitation, Mayo exercise, is not a completely harmless activ- Clinic, 200 First St SW, Rochester, MN 55905. ity that can be performed with abandon. We have observed that older patients with age-related degenerative changes were the REFERENCES most affected. When the musculoskeletal 1. Hayes M, Chase S. Prescribing yoga. Prim Care. 2010;37(1):31-47. structure is challenged with strenuous yoga 2. Cramer H, Ward L, Steel A, Lauche R, Dobos G, Zhang Y. Prevalence, patterns, and predictors of yoga use: results of a in the setting of aging or other connective U.S. nationally representative survey. Am J Prev Med. 2016; tissue disorders, injuries can occur. 50(2):230-235. 3. Saper RB, Eisenberg DM, Davis RB, Culpepper L, Phillips RS. We are not proposing that patients quit Prevalence and patterns of adult yoga use in the United States: yoga. We agree that yoga can improve bal- results of a national survey. Altern Ther Health Med. 2004;10(2): ance, provide an environment for socializing, 44-49. 4. McArthur C, Laprade J, Giangregorio LM. Suggestions for and help reduce stiffness. Rather, we are sim- adapting yoga to the needs of older adults with osteoporosis. ply recommending that patients modify their J Altern Complement Med. 2016;22(3):223-226. 5. Lu YH, Rosner B, Chang G, Fishman LM. Twelve-minute daily poses to better accommodate their physical yoga regimen reverses osteoporotic bone loss. Top Geriatr limitations. As the body changes over time, Rehabil. 2016;32(2):81-87. exercise regimens need to be modified as 6. Swain TA, McGwin G. Yoga-related injuries in the United States from 2001 to 2014. Orthop J Sports Med. 2016;4(11): well to protect the spine, shoulders, hips, 2325967116671703. and other musculoskeletal structures. 7. Sinaki M. Yoga spinal flexion positions and vertebral compres- sion fracture in osteopenia or osteoporosis of spine: case series. Pain Pract. 2013;13(1):68-75. CONCLUSION 8. Tüzün S, Aktas I, Akarirmak U, Sipahi S, Tüzün F. Yoga might be To our knowledge, this report describes the an alternative training for the quality of life and balance in post- menopausal osteoporosis. Eur J Phys Rehabil Med. 2010;46(1): largest case series of medically documented 69-72. yoga-related injuries to date. Yoga poten- 9. Wright NC, Looker AC, Saag KG, et al. The recent prevalence tially has many health benefits, but it is not of osteoporosis and low bone mass in the United States based on bone mineral density at the femoral neck or lumbar spine. without risk. As evidenced by this case se- J Bone Miner Res. 2014;29(11):2520-2526. ries, many injuries can still occur, even in 10. Sfeir JG, Drake MT, Sonawane VJ, Sinaki M. Vertebral compres- sion fractures associated with yoga: a case series. Eur J Phys long-term yoga practitioners. Care must be Rehabil Med. 2018;54(6):947-951. taken, particularly when performing posi- 11. Cramer H, Ostermann T, Dobos G. Injuries and other tions with extreme spinal flexion and adverse events associated with yoga practice: a systematic re- view of epidemiological studies. J Sci Med Sport. 2018;21(2): extension. Patients with osteopenia or osteo- 147-154. porosis may have a higher risk of compres- 12. Campo M, Shiyko MP, Kean MB, Roberts L, Pappas E. Muscu- loskeletal pain associated with recreational yoga participation: sion fractures or deformities. As yoga gains a prospective cohort study with 1-year follow-up. J Bodyw popularity, the prevalence of yoga-related in- Mov Ther. 2018;22(2):418-423. juries is also expected to increase. Physicians 13. Sinaki M, Itoi E, Rogers JW, Bergstralh EJ, Wahner HW. Corre- lation of back extensor strength with thoracic kyphosis and are encouraged to discuss such risks with lumbar lordosis in estrogen-deficient women. Am J Phys Med their patients when asked about the safety Rehabil. 1996;75(5):370-374.

430 Mayo Clin Proc. n March 2019;94(3):424-431 n https://doi.org/10.1016/j.mayocp.2018.09.024 www.mayoclinicproceedings.org SOFT TISSUE AND BONY INJURIES ATTRIBUTED TO YOGA

14. Sinaki M, Itoi E, Wahner HW, et al. Stronger back muscles 19. Rohlmann A, Graichen F, Weber U, Bergmann G. 2000 Volvo reduce the incidence of vertebral fractures: a prospective 10 Award winner in biomechanical studies: monitoring in vivo year follow-up of postmenopausal women. Bone. 2002;30(6): implant loads with a telemeterized internal spinal fixation de- 836-841. vice. Spine (Phila Pa 1976). 2000;25(23):2981-2986. 15. Yung PS, Lai YM, Tung PY, et al. Effects of weight bearing and 20. Melton LJ III, Khosla S, Atkinson EJ, O’Connor MK, non-weight bearing exercises on bone properties using calcaneal O’Fallon WM, Riggs BL. Cross-sectional versus longitudinal quantitative ultrasound. Br J Sports Med. 2005;39(8):547-551. evaluation of bone loss in men and women. Osteoporos Int. 16. Sinaki M, Pfeifer M, Preisinger E, et al. The role of exercise in the treat- 2000;11(7):592-599. ment of osteoporosis. Curr Osteoporos Rep. 2010;8(3):138-144. 21. Sinaki M, Limburg PJ, Wollan PC, Rogers JW, Murtaugh PA. 17. Sinaki M, Mikkelsen BA. Postmenopausal spinal osteoporosis: Correlation of trunk muscle strength with age in children 5 flexion versus extension exercises. Arch Phys Med Rehabil. to 18 years old. Mayo Clin Proc. 1996;71(11):1047-1054. 1984;65(10):593-596. 22. Sinaki M, Nwaogwugwu NC, Phillips BE, Mokri MP. Effect 18. Itoi E, Sakurai M, Mizunashi K, Sato K, Kasama F. Long-term ob- of gender, age, and anthropometry on axial and appendic- servations of vertebral fractures in spinal osteoporotics. Calcif ular muscle strength. Am J Phys Med Rehabil. 2001;80(5): Tissue Int. 1990;47(4):202-208. 330-338.

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